TABLE OF CONTENTS Viewing computer systems at the digital logic level exposes us to the nuts and bolts of the basic hardware. The goal of this chapter is to cover the necessary digital logic background. Our discussion can be divided into three parts. In the first part, we focus on the basics of digital logic circuits. We start off with a look at the basic gates such as AND, OR, and NOT gates. We introduce Boolean algebra to manipulate logical expressions. We also explain how logical expressions are simplified in order to get an efficient digital circuit implementation.
The second part introduces combinational circuits, which provide a higher level of abstraction than the basic circuits discussed in the first part. We review several commonly used combinational circuits including multiplexers, decoders, comparators, adders, and ALUs.
In the last part, we review sequential circuits. In sequential circuits, the output depends both on the current inputs as well as the past history. This feature brings the notion of time into digital logic circuits. We introduce system clock to provide this timing information. We discuss two types of circuits: latches and flip-flops. These devices can be used to store a single bit of data. Thus, they provide the basic capability to design memories. These devices can be used to build larger memories, a topic covered in detail in the next chapter.
A computer system has three main components: a...
